Abstract

Nitrogen physical adsorption at 77.5 and 80.4 K on a standard graphite was studied with the purpose too analyze adsorption models and to determine nitrogen cross-sectional areas for each model. With this intention different models, such as Van der Waals, Langmuir, and BET, which describe the adsorption process at different surface coverages were employed. Molar differential entropies and isosteric heats of adsorption were calculated. A two-dimensional phase transition was confirmed. Adsorbed molecule cross-sectional areas were determined at different surface coverages, by direct comparison with that corresponding to argon. The values obtained varied in a wide range (0.135 to 0.166 nm2) depending on surface coverage.